Frequencies for first 10,000 rows of congen variable in natl1970 dataset :

 Congenital |
Malformatio |
          n |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |      9,923       99.23       99.23
          1 |         77        0.77      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016